Television and/or radio operators and their advertisers may benefit when a commercial advertisement (an ad) can be targeted to a specific audience. For example, it may be financially advantageous to insert customized or local television (TV) ads into entertainment or news programming at local broadcast stations, or even to insert custom ads at a metropolitan media head end in the case of cable television. Media delivery may include the broadcast and reception of a video or an audio program. A video program may include video samples comprising a television, cable, or satellite broadcast. Similarly, an audio program may include audio samples comprising a radio broadcast or a public address broadcast. Some media broadcasters charge media recipients directly, and may use a “pay per view” revenue model where access to a particular program is granted, or they may use a subscription revenue model where access is granted for a period of time based on the subscription agreement. In order to prevent reception of a broadcast by an unauthorized recipient it is now common to encrypt or “scramble” the program data so that only authorized receivers (i.e. those who have paid) will be granted access.
The insertion of an advertisement into a program can be termed ad splicing, which is increasingly considered an important source of revenue for media broadcasters. However, encryption of media content has complicated the implementation of ad splicing. Currently, custom ads are multiplexed into a program that may be scrambled or encrypted using a conditional access system (CAS), since the CAS is typically local and co-resident with the ad multiplexing. To simplify decryption, both the program content and the advertising content are typically encrypted together.